Hydrotrephes langkawicus, Zettel & Tran, 2009

Zettel, Herbert & Tran, A. D., 2009, First Inventory Of The Water Bugs (Heteroptera: Nepomorpha: Gerromorpha) Of Langkawi Island, Kedah, Malaysia, Raffles Bulletin of Zoology 57 (2), pp. 279-295 : 282-284

Hydrotrephes langkawicus , new species

( Figs. 2, 6-12 )

Material examined. – Holotype (macropterous male) and paratypes (1 hindwing-micropterous female, 3 macropterous males, 2 macropterous females), HZL9 , labeled “ MALAYSIA, Kedah \ C-Langkawi, S slopes\ of Gn. Raya, lowland\ stream, 22.11.2006 \ leg. H. Zettel ( HZL9 )”, holotypes and paratypes in NHMW, 1 paratype male in ZRC.

Description of macropterous male. – Habitus: see Figure 2 . Body size: length 1.9–2.0 mm, width 1.35–1.40 mm.

Colour: Yellow with extended dark brown markings on dorsum, especially on head ( Figs. 2, 6 ). Venter mostly brownish. Legs and antennae yellow; rostrum light brown.

Cephalonotum with lateral margins behind eyes slightly concave in dorsal view; sharp margin of pronotal part ending in short distance from posterolateral corner and there forming a small, rather blunt angulation; head with densely set small punctures, with very narrow interspaces, almost dull; disk of pronotum set with numerous very fine micropunctures, and with scattered, unequally distributed and somewhat larger punctures becoming denser towards sides. Mesoscutellum 0.9 times as long as wide, with puncturation of similar size, but slightly denser than on disk of pronotum, micropunctures medially obliterated. Hemelytron with slightly stronger puncturation, interspaces shagreened and dull. Genal plate stout; pronotal plate ( Fig. 7 ) with shallow incision, anteriorly relatively wide. Inner corner of propleural plate broadly convex. Eye index: 2.1–2.2. Fourth rostral segment 2.3 times as long as segment 3.

Ventral carinae ( Fig. 8 ): Prosternal carina with posterior corner approximately rectangular, with posterior edge slightly concave; apices of meso- and metasternal carina thin-laminate, that on mesosternum strongly reduced; carina of sternite 3 with few small denticles, the proximal one variably enlarged. Abdominal segments strongly asymmetrical.

Aedeagus ( Fig. 9 ) moderately slender, apically rather stout and slightly bent to right side; with narrow apical plate posteriorly extended into short spine. Right paramere ( Fig. 10 ) shorter than left paramere, slender-lanceolate, curved, apex minutely pointed. Left paramere ( Fig. 11 ) moderately slender, distally evenly narrowed and slightly curved, apex narrowly rounded.

Description of macropterous female. – Body size: length 2.1–2.2 mm, width 1.46–1.49 mm. Eye index: 2.1. Most characteristics similar to that of male, except the following. Abdomen symmetrical. Sternite 6 with concave hind margin. Subgenital plate ( Fig. 12 ) with broad mediodistal lobe with broadly convex hind margin; inner ridge strongly concave, almost semicircular. Ventral laterotergites 8 slender.

Hindwing-micropterous female: body size: length 2.1 mm, width 1.42 mm; eye index: 2.6; pronotum with posterolateral corners less elevated and with angulation of lateral margin more blunt; hemelytron without embolar and claval sutures; other characteristics as in brachypterous female.

Hindwing-micropterous male: unknown.

Etymology. – Named after the island of type locality. The species epithet is a Latinized adjective.

Remarks. – This species belongs to the Hydrotrephes martini group as defined by Zettel (2000a). Hitherto, this species group contained eight described species, distributed on the islands of Borneo (five species), Sumatra, Siberut, and Nias (one species each) ( Zettel, 2004a; Papá ek & Zettel, 2005). Hydrotrephes langkawicus , new species is one of the smallest species of the genus; in the H. martini group only H. nitidus Zettel, 2004 , a strongly shiny species with deeply emarginate prosternal carina, is of similar size. The genital structures of the male of H. langkawicus are characteristic. Further, the combination of the weakly emarginate prosternal carina, the reduced lamina on the mesosternal carina, and the lobate subgenital plate of the female is unique.

Distribution. – Only known from the type locality on Langkawi Island.

Figures

Figs. 2–6. Habitus of (2) Hydrotrephes langkawicus, new species (macropterous male, paratype). (3) Strongylovelia narusei, new species (apterous female, paratype). (4) Microvelia (Picaultia) minutissima, new species (apterous female, paratype). (5) Microvelia (Picaultia) minutissima, new species (macropterous male, holotype, right forewing broken off). (6) Frontal view of cephalonotum of Hydrotrephes langkawicus, new species (macropterous male, paratype).

Figs. 7–12. Hydrotrephes langkawicus, new species: 7, genal and pronotal plate; 8, ventromedian carina of thorax and abdomen, with variations of prosternal carina, mesosternal carina, and carinae of sternites 2 and 3; 9, aedeagus, right view; 10, right paramere, right view; 11, left paramere, right view; 12, sternite 7 of female, ventral view, pilosity omitted.